Since a double-walled carbon nanotube (DWCNT)-based rotary motor driven by a uniform temperature field was proposed in 2014, how to control quantitatively the rotation of the rotor is still an open question. In this work, we present a mathematical relationship between the rotor's speed and interaction energy. Essentially, the increment of interaction energy between the rotor and the stator(s) determines the rotor's rotational speed, whereas the type of radial deviation of an end carbon atom on the stator determines the rotational direction. The rotational speed of the rotor can be specified by adjusting temperature and radial deviation of an end carbon atom on the stator. It is promising for designing a controllable temperature-driven rotary motor based on DWCNTs with length of few nanometers only.